The present invention relates in general to the absorption of energy associated with a an explosion or sudden impact, and, in particular, to reducing the amount of force (acceleration) transmitted to a seated occupant as a result of a mine blast.
There is currently a great deal of interest in improving the safety of vehicles subject to mine blast loading. Land mine explosions pose two serious threats to vehicle occupants. First, the mines may contain projectiles which penetrate the underside of the vehicle and strike the occupants. Secondly, the blast energy can cause very high accelerations to be imparted to the occupants. Many research efforts have centered on adding armor to the underside of a vehicle to reduce the penetration of projectiles and to either divert or absorb the energy associated with a mine blast event. However, the ultimate goal is to protect the individual occupants. The most efficient way to provide this protection, within space and weight limitations, may be to provide local protection to each individual occupant.
The current seat configuration for the Army's M923A2 5-ton truck is shown in FIG. 1. The seat 10 is attached to a pedestal 12 which is attached to the vehicle floor 13. The seat pedestal 12 contains an assembly 15 to adjust the location of the seat. The occupant 14 is attached to the seat with a four point restraint system (not shown) to provide stability in the event of an accident. In the event of a land mine blast, this seat configuration can transmit a great deal of the blast energy to the occupant 14.
In a Jun. 3, 1994 test of the M923A2 5-ton truck subject to a land mine explosion under the driver, the mannequin in the driver's seat was subject to an acceleration of 75 times that of gravity for 1 millisecond, and sustained accelerations of approximately 25 times the acceleration of gravity for over 30 milliseconds. See P. C. Chan, K. K. Kan, D. W. Long, and J. H. Stuhmiller, "Soldier Vulnerability to Land Mine Explosions," JAYCOR Final Report for U.S. Army Communications and Electronics Command (CECOM), Night Vision and Electronic Sensors Directorate, Fort Belvoir, Va., Contract Number DAAK70-94-C-0012, April 1995. These accelerations were measured by accelerometers in the mannequin's pelvis and neck regions and are clearly above the threshold for serious spinal injury to humans.